The present invention relates to improvements in tablet manufacture and to tablets manufactured by the process of this invention.
More specifically, the invention relates to an improved tablet formulation that permits the manufacture of effervescent sub-lingual type tablets in a normal or ambient environment and at the same time resulting in tablets that are less affected by atmospheric humidity. The invention also relates to a method or process for manufacturing such products.
The present invention permits the manufacture of effervescent sub-lingual type tablets that are designed to be placed under the tongue and sucked until completely dissolved. This technique of administration is similar to conventional sub-lingual tablets which allow for fast absorption of the pharmaceutically or therapeutically active ingredients from the stomach.
The value of sub-lingual tablets has been recognized for many years as a very effective dosage form that permits the active ingredient(s) to be quickly utilized by the body.
This is of particular value where rapid availability of the active ingredients is desired. For example glyceryl trinitrate sub-lingual tablets are prescribed for patients suffering from the acute anginal pain, in the long term management of angina pectoris and in cardiac emergencies. An essential pre-requisite is that the active ingredient must be rapidly released while in the mouth, otherwise the needed quick relief is not achieved.
However, a common feature of sub-lingual tablets is poor palatability. Because of the effervescent base, and the inclusion of flavours, the novel formulae of the present invention not only assures dissolution of the tablets in saliva by releasing the active ingredients as a microsuspension that facilitates prompt absorption but also provides a pleasant taste which reduces any patient resistance.
This feature is of particular value with products formulated for children.
Effervescence is achieved by including an acid, for example, citric acid and/or tartaric acid, and an effervescing alkali, for example sodium bicarbonate, potassium bicarbonate and/or calcium carbonate, in the formula. In the presence of traces of water, these ingredients react, forming bubbles of carbon dioxide and liberating more water that further promotes the reaction. Depending on the nature of the active ingredient(s), which may be either soluble in water or are converted to the sodium salt(s) which are then dissolved, all ingredients of effervescent sub-lingual tablets are typically dissolved before ingestion.
Generally, the amount of moisture in the atmosphere is sufficient to start this reaction, so a very low relative humidity, typically less than 10%, in the environment is required for all processing and packaging stages. Further, it has often been necessary to individually wrap each tablet to protect it from moisture during packaging and distribution.
It is an object and an advantage of the present invention to provide an effervescent sub-lingual type tablet and a method or process of manufacturing same which goes at least some way towards overcoming or at least minimizing the prior art problems or limitations outlined above, or for providing a clear alternative choice for customers.
It is another object and advantage of this invention to provide an effervescent sub-lingual tablet and a method or process of manufacturing same which is relatively stable under normal or ambient conditions.
It is a further object and advantage of this invention to provide an effervescent sub-lingual type tablet formulation, where the manufacture thereof is possible in an environment wherein no special precautions (apart from mechanical ventilation) have been taken to minimize the relative humidity of the air during the processing and the packaging thereof.
It is yet another object and advantage of this invention to provide a sub-lingual type tablet formulation which does not require any special protection from atmospheric moisture during subsequent storage, or packaging and storage both before and after sale.
These and other objects of this invention will become more apparent from the following description.
According to one aspect of the invention there is provided an effervescent sub-lingual type composition, and especially a flavored effervescent tablet composition or formulation, which includes at least one active ingredient, one or more fruit acids, e.g., citric acid or tartaric acid and one or more effervescing alkalis, e.g., sodium bicarbonate, potassium bicarbonate and/or calcium carbonate, amongst the active ingredients of the composition, wherein the acid component(s) of the composition has been pre- or post-coated with a protective layer of a polydimethylsiloxane which substantially minimises contact between the acid and atmospheric moisture until the composition is purposely mixed with water.
According to another aspect of the invention there is provided a method of preparation of an effervescent composition, and especially an effervescent medicinal or therapeutic composition, wherein the acid(s) or other effervescing components are pre-coated with a polydimethylsiloxane before the coated component is further mixed with the other composition ingredients.
Preferably, the pH of the polydimethylsiloxane is similar to that of the acid component, typically pH 2-3. Preferably, the concentration of the polydimethylsiloxane varies in the range of about 0.05 to about 1.5% of the total weight of the composition.
The pre-coating of the effervescent acid component(s) of the composition effectively precludes any reaction with the alkali component(s) because of the atmospheric moisture, even when the relative humidity of the air is more than about ten percent (10%).
Further, compressed tablets manufactured according to the invention do not require any special protection from atmospheric moisture during subsequent storage, packaging and storage both before and after sale.
Preferably, according to the invention, the acid is loaded into the mixing bowl of a granulating machine fitted with a two speed planetary mixing blade and separate horizontally mounted high speed chopper mixer. The polydimethylsiloxane is added and the conventional mixing blade is switched on, with high speed being selected. Mixing continues until all of the acid has been coated with this material and a damp, solid mass has been formed. After this has been achieved, the chopper-mixer of the machine is switched on and the mass is subjected to this treatment for about 0.5 to 1.0 minutes, followed by about a further 2-5 minutes of high speed mixing by the planetary blade.
The mixture is then discharged from the granulating machine onto stainless steel trays in thin layers. These trays are then loaded into a drying oven preheated to and set at 50 degrees Centigrade for about 18 hours to dry. It is then reloaded into the granulating machine.
According to one embodiment using citric acid and using a Karl Fischer Titrator apparatus, the maximum water content of the coated citric acid is 0.2% w/w.
The other ingredients in the formula including the effervescing alkali(s) are added to the granulating machine, which is then switched on, using the planetary mixing blade at high speed, for about 305 minutes. The dry mixture is then unloaded and compressed into tablets.